(1) Field of the Invention
The present invention relates to a power supply apparatus having a back-up battery for supplying a power to a load, which power supply apparatus is used in, for example, computers.
Computers are now required to continue operation even when a power failure or an instantaneous power cut occurs, and to this end, various back-up method are conventionally provided.
(2) Description of the Related Art
In the conventional power supply apparatus for supplying a power to a load, a back-up battery is directly connected to the output of an AC/DC converter. During a period when the AC/DC converter generates a DC current, the battery is charged up, and when the AC/DC converter does not generate a DC current, the charged-up battery supplies power to the device.
When a work in the load is finished, and when an operator manually turns off a circuit breaker for turning the power supply apparatus on or off, the output from the AC/DC converter becomes zero volts and the situation becomes the same as that when a power failure occurs, with the result that the battery automatically executes a back up operation.
Therefore, even when a power failure or a fault in the AC/DC converter does not occur, the back-up operation is executed every time the circuit breaker is manually turned off, and this causes a problem in that the shortening the life of the battery is accelerated.